1. Field of the Invention
The invention relates to a control apparatus of an automatic transmission mounted in a vehicle. More specifically, the invention relates to a control apparatus which promptly establishes and outputs a shift command when a downshift is to be performed through a plurality of speeds.
2. Description of the Related Art
Typically, an automatic transmission mounted in a vehicle shifts speeds based on a demand for acceleration by a driver, the running state of the vehicle, and the operating state of the automatic transmission, and the like. For example, when the driver deeply depresses the accelerator, the speed is calculated based on that depression amount, the throttle opening amount, and the vehicle speed and the like, and a downshift (i.e., a shift toward the deceleration side) is performed. Technology is known that executes shift control according to a predetermined shift pattern as shift control of an automatic transmission.
For example, Japanese Patent Application Publication No. 5-99314 (JP-A-5-99314) describes a control apparatus of an automatic transmission that performs optimum shift logic (i.e., shift output) when shifts according to various shift patterns are to be performed. This control apparatus has a main shift unit and an auxiliary shift unit to which the main shift unit is connected. The control apparatus uses the main shift unit and the auxiliary shift unit to establish multiple speeds. The control apparatus also includes means for detecting a running condition of the vehicle; shift determining means for receiving a signal indicative of the running condition, making a shift determination, and generating a shift determination signal; a shift pattern table that typifies the kinds of shifts into a plurality of shift patterns and provides shift logic for each shift pattern; pattern selecting means for receiving the shift determination signal generated by the shift determining means and selecting the optimum shift logic referencing the shift pattern table; shift setting means for setting a shift corresponding to the shift logic that was selected by the pattern selecting means; and a hydraulic control circuit that receives a shift signal generated by the shift selecting means and selectively supplies and drains hydraulic fluid to and from a hydraulic servo of each of a plurality of frictional engagement elements.
According to the control apparatus described in the foregoing publication, the optimum shift logic for each type of shift can be performed. As a result, the shift duration can be prevented from increasing and shift shock can be prevented from occurring.
However, in the control apparatus described in the foregoing publication, the next shift is predicted by a change in the throttle opening amount. Also, when starting a shift through a plurality of speeds, a shift command for an appropriate speed is output after a predetermined period of time has passed according to a timer such that the shift command is not output in an intermediate speed.
At this time, the timer operates from the time a speed other than the currently selected speed was established as a target speed based on the throttle opening amount until a predetermined period of time has passed.
The predetermined period of time is set uniformly taking into account the various shift modes such as a downshift through a plurality of speeds such as third speed or second speed. Therefore, in order to prevent shift logic for an intermediate speed from being performed, the predetermined period of time must be set longer. As a result, it takes more time for a shift command to be output.